[rbridge] Consensus Check: MAC learning timers

[James Carlson]

Joe Touch writes:
> James Carlson wrote:
> > Lacking a clear interoperability issue for TRILL itself, SHOULD seems
> > right to me.  It means that implementations are required to follow
> > that IEEE standard unless they've got a good reason to do otherwise.
> 
> I'd say MUST follow IEEE requirements.

Where's the TRILL requirement for this?

I'm saying SHOULD because our role here isn't to design IEEE
protocols, nor is it to "enforce" any rules set down by IEEE.

Instead, our role is to design TRILL, and specify what's _required_ to
make that work.  Is there an issue here that, if someone had a good
reason to use some other set of defaults for these parameters, doing
so would break TRILL?

If there's no such issue, then we don't need a "MUST."  Following the
IEEE norms becomes just an issue of good practice, and not a
fundamental requirement of the protocol.

I'm not talking about people who wantonly ignore standards.  There's
nothing we can do about that situation -- they'll ignore MUST just as
easily as they'll ignore the implication of SHOULD.  I'm talking about
requirements for TRILL itself.

> I'm wondering how the IEEE spec's the defaults; if they're a MUST, then
> why wouldn't we follow suit? How would we know what would break with
> intermediate bridges? If, alternately, the defaults are SHOULDs, then
> ours can be too.
> 
> I don't think it would be useful to diverge from those specs except
> where we deliberately need to.

I'm not suggesting creating a divergence in actual values.  I'm
suggesting that we don't need to copy the IEEE language into the TRILL
documents _unless_ there's a specific TRILL-related issue to solve.

Using SHOULD doesn't actually diverge us from IEEE, even if they use
MUST.  It provides leeway for a savvy implementor to spurn IEEE's
mandate for the good of TRILL, _if_ that's actually the right thing to
do.  It still requires others to follow IEEE if they don't have that
"good reason."

-- 
James Carlson, Solaris Networking              <james.d.carlson at sun.com>
Sun Microsystems / 1 Network Drive         71.232W   Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757   42.496N   Fax +1 781 442 1677